JP5441480B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition for a wet brake suitable as a common lubricating oil for agricultural tractors and construction machinery vehicles having excellent wet brake friction characteristics, wear resistance and oxidation stability.

  Agricultural tractor wet braking systems require braking performance commensurate with pedaling force, but at the same time, the friction part is also required to prevent abnormal noise and abnormal vibration caused by sliding. Specifically, a higher coefficient of static friction is preferable for braking performance, but it is likely to cause squeal and abnormal vibration due to a stick-slip phenomenon immediately before stopping. Therefore, if the friction coefficient is increased when the sliding speed is high, such as at the start of braking, and the static friction coefficient is low when the braking speed is low, good brake stop performance and stick-slip resistance can be achieved. It will be compatible.

  If the friction characteristics are classified in this way, the dynamic friction coefficient is high in order to achieve both good brake stop performance and stick-slip resistance, and if the static friction coefficient is low, the value of μs / μd becomes small. If the stick-slip resistance is poor, the dynamic friction coefficient is low, the static friction coefficient is high, and the value of μs / μd is large.

  In general, a friction modifier (FM) is blended in order to impart necessary friction characteristics to the lubricating oil for wet clutches and wet brakes. As the friction modifier, fatty acids, ester compounds, alcohol compounds, amine compounds, amide compounds, phosphorus compounds, sulfur compounds, solid lubricants, and the like are used.

  The friction modifier adsorbs on the surface of the brake material or clutch material to form an adsorbed film, and the frictional resistance / peeling resistance between the films becomes the frictional force. If the adsorbing force is large, the frictional force increases. . On the other hand, if the attractive force is small, the frictional force becomes small as a result of being easily peeled off. The wet friction characteristic determines how much the adsorption force changes depending on whether the sliding speed is large or small, and is related to the dynamic friction coefficient and the static friction coefficient.

  Fatty acids have excellent adsorption properties, but have poor thermal oxidation stability and poor water separation. The blending of other ester compounds, alcohol compounds, and amide compounds differs in lipophilicity and adsorption power depending on the structure of each compound. That is, ester compounds have a problem of hydrolyzability when mixed with water, amine compounds tend to generate lacquer at high temperatures, and alcohol compounds have weak lipophilicity as FM. Has a point.

  Examples of the wet brake lubricant composition include Patent Document 1 and Patent Document 2, and in the former, acidic phosphate ester amine salt, oleic acid, oleic acid diethanolamide, oleic acid triglyceride and stearyl alcohol are cited as friction modifiers. On the other hand, in the latter, ethers and phosphate compounds of higher alcohols having 8 or more carbon atoms and glycerin are introduced. In Patent Document 3, a combination of diol and phosphate is introduced as a friction modifier.

Japanese Patent Laid-Open No. 6-200269 JP 2004-204002 A Japanese Patent No. 4132280

  As described above, the present invention, for example, an agricultural tractor having a friction characteristic that increases the dynamic friction coefficient when the sliding speed is high, such as when the brake is applied, and has a low static friction coefficient when the speed at which the brake stops is low. It is an object of the present invention to provide a lubricating oil composition that is effective in wet braking systems for large vehicles such as the above and has both brake stop performance and stick-slip resistance.

In the first aspect of the present invention, mineral oil and synthetic oil are used as base oils, and (A) an aliphatic 1,2-diol compound represented by the following general formula (formula 1) is 0.01 to 0.3 based on the total amount of the composition. % By weight, and (B) 0.05 to 5% by weight of dialkenyl hydrogen phosphite represented by the general formula (Formula 2) based on the total amount of the composition, The present invention relates to a lubricating oil composition for wet brakes having a ratio of 0.8 or less.
C _n H _2n + _{2 O} 2 or _C n _H 2n _{O 2} (Formula 1)
(The carbon number n is 12 to 16)
(RO) ₂ PH = O (Formula 2)
(R is an alkenyl group having 14 to 18 carbon atoms)
The second aspect of the present invention relates to the lubricating oil composition for wet brakes according to claim 1, wherein the dialkenyl hydrogen phosphite is dioleoyl hydrogen phosphite.
According to a third aspect of the present invention, the wet brake lubricating oil composition according to claim 1 or 2 further comprises a metal detergent dispersant, an ashless dispersant, a zinc dialkyldithiophosphate, a hindered phenol antioxidant, an amine. The present invention relates to a lubricating oil composition for wet brakes containing at least one type of antioxidant, sarcosine rust inhibitor, polymethacrylate viscosity improver and silicone antifoaming agent.

  An object of the present invention is to provide a lubricating oil composition which is effective as a lubricant for a wet brake system for a large vehicle such as an agricultural tractor and has both improved brake stop performance and stick-slip resistance.

  The present invention relates to the improvement of the prior art as described above, and as a result of earnest research to overcome the problems of alcohol compound friction modifiers, alcohol compound friction modifiers having a special structure and In combination with a specific phosphate ester, the ratio of the friction coefficient of 3 mm / s to the friction coefficient of 38 mm / s, that is, the ratio of μ3 / μ38 at 40 ° C. is 0.8 or less, preferably 0.5 -0.8, more preferably 0.6-0.8, it has been found that it has not only brake performance but also excellent stick-slip resistance, and a lubricating oil composition for wet brakes using this I came to discover things.

  The composition of the present invention will be described in detail. One embodiment thereof is a mineral lubricating oil having a viscosity of about 1 to 50 cSt at 100 ° C. or a refined product thereof (hereinafter referred to as “mineral oil”) and a viscosity of about 1 at 100 ° C. Mineral oil or hydrocarbon-based synthesis of the alcohol component (A) represented by the formula 1 in a proportion of 0.01 to 0.3% by mass with respect to a lubricating base oil selected from a synthetic lubricating oil base of ˜50 cSt It is blended with oil. If it is less than this, the original effect will not be exhibited, while if it is more, the solubility in oil may be problematic. If a small amount of ester is added to increase the solubility, the amount added can be further increased. Moreover, since it is not necessary to completely dissolve in the base oil for applications such as grease, the amount added can be further increased.

C _n H _{2n + 2} O ₂ or C _n H _2n O ₂ (the carbon number n is 12 to 16) (formula 1)

The aliphatic alcohol component is specifically an aliphatic 1,2-diol having 12 to 16 carbon atoms and having two OH groups. The aliphatic part may be either an alkyl group or an alkenyl group.
Examples thereof include 1,2-dodecanediol, 1,2-tridecanediol, 1,2-tetradecanediol, 1,2-pentadecanediol, and 1,2-hexadecanediol.

And the phosphorus compound (B) shown by Formula 2 is made to contain 0.05 to 5 mass% on the basis of the total amount of the composition.
(RO) ₂ PH = O (Formula 2)
(R is an alkenyl group having 14 to 18 carbon atoms)
Since this dialkenyl hydrogen phosphite is less acidic than an acidic phosphate ester, it has a feature that does not impair the oxidation stability of the lubricating oil. Dioleyl hydrogen phosphite is particularly preferable.

  If both of the above components (A) and (B) are too small, the effect of addition will not be sufficiently exhibited, and if the amount is too large, improvement of the effect cannot be expected, which is disadvantageous because of high costs. . They discovered that performance can be improved synergistically by combining them, not alone.

  In addition to the above components (A) and (B), the lubricating oil composition of the present invention includes known additives that are usually used depending on the purpose, such as metal detergent dispersants, ashless dispersants, and seizures. Antiwear agents, antioxidants, corrosion inhibitors, viscosity index improvers, pour point depressants, antifoaming agents and the like are blended.

As the mineral base oil of the present invention, specifically, the lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil is subjected to solvent desorption, solvent extraction, hydrogen A method of isomerizing GTL WAX (gas-tri-liquid wax) produced by one or more treatments such as decomposition, solvent dewaxing, hydrorefining, etc., or wax isomerized mineral oil, Fischer-Tropsch process, etc. Examples of the lubricant base oil to be manufactured can be given.
Synthetic oils include, for example, poly α-olefin (PAO), α-olefin copolymer, polybutene, alkylbenzene, polyol ester, dibasic acid ester, polyoxyalkylene glycol, polyoxyalkylene glycol ester, polyoxyalkylene glycol ether. , Hindered esters, silicone oils and the like. As described above, these synthetic oils can be used alone or in combination of two or more, and further, mineral oil and synthetic oil can be used in combination.

  Examples of metal detergent dispersants include alkaline earth metal sulfonates and alkaline earth metal phenates. Examples of ashless dispersants include alkenyl succinimides, alkenyl succinates, amides of long-chain fatty acids and polyamines (aminoamide type), and the like. However, seizure wear inhibitors include sulfurized fats and oils, sulfurized olefins, sulfides, phosphate esters, phosphite esters, thiophosphate esters, etc., and antioxidants such as amine and phenolic antioxidants are corrosive. Examples of the inhibitor include benzotriazole and alkenyl succinate, polymethacrylate and olefin copolymer as the viscosity index improver, polymethacrylate as the pour point depressant, silicon compound as the antifoaming agent, Examples thereof include ester-based antifoaming agents.

The wet friction characteristics were evaluated in accordance with the friction test method (JCMAS P 0474) using the micro-clutch tester of the Japan Construction Mechanization Association / Hydraulic hydraulic fluid for construction machinery-Friction characteristics test method (JCMAS P 047: 2004). Was done.
The detailed test method of the micro clutch test is shown below.
[Specimen material]
Clutch disc facing material: D-0512 (JASO M349 material)
Plate material: SS400
[Test conditions]
Temperature: 40 and 80 ° C
Surface pressure: 1MPa
Sliding speed: 3.0 and 38.0 mm / s
Friction time: 5 min
Hereinafter, the present invention will be described by way of examples, reference examples, and comparative examples under the above microclutch test conditions, but these are merely examples, and the present invention is not limited thereto.

[Examples 1-2, Reference Examples 1-5, and Comparative Examples 1-5]
Commercial oil for tractors (package additive containing overbased calcium sulfonate, zinc di-2-ethylhexyl dithiophosphate, triphenyl phosphite, polybutenyl succinimide, succinate) was used as Comparative Example 1, and this oil Example 1 in which 0.2% by mass of each of alcohol compounds 1, 2, and 3 was added to Example 1, 1 and 3 in which Reference Example 2 was combined with a phosphorus compound, and Comparative Example 1 in which alcohol compounds 4, 5, and 6 were combined. Comparative Examples 2, 3, 4, 5 in which 0.2% by mass of 7 was added, and Reference Examples 4, 5, and 0.1% in which 0.1% by mass and 0.3% by mass of alcohol compound 2 were added to Comparative Example 1 Example 2 was prepared by combining 5 with 0.2% by mass of a phosphorus compound. The components and properties of Comparative Example 1 are shown in Table 1, and the formulations of Examples, Reference Examples and Comparative Examples are shown in Table 2 and Table 3.

(A) Alcohol compound and (B) Phosphorus compound used in Examples and Comparative Examples Alcohol compound 1: 1,2-tetra / hexadecanediol mixed Alcohol compound 2: 1,2-hexadecanediol Alcohol compound 3: 1, 2- Dodecanediol Alcohol compound 4: 1-Hexadecanol Alcohol compound 5: 1-Dodecanol Alcohol compound 6: 1-Octanol Alcohol compound 7: 1,2-Octanediol Phosphorus compound: Dioleyl hydrogen phosphite

ここで比較例１の市販トラクターオイルは、過塩基性カルシウムスルホネート、ジ−２−エチルヘキシルジチオリン酸亜鉛、トリフェニルホスファイト、ポリブテニルコハク酸イミド、コハク酸エステルが含まれるパッケージ添加剤６質量％とポリメタアクリレート系の粘度指数向上剤６質量％を基油（鉱油系基油、動粘度が５．９５ｍｍ^２／ｓ ＠１００℃ および３７．５ｍｍ^２／ｓ ＠４０℃）に添加して調整したもので、さらにポリメタアクリレート系の流動点降下剤を外割で０．１質量％および泡立ち防止剤としてシリコーン系消泡剤を１０ｐｐｍ添加している。 Comparative Example 1 Commercial Tractor Oil Properties and Its Constituents

Here, the commercial tractor oil of Comparative Example 1 is an overbased calcium sulfonate, zinc di-2-ethylhexyl dithiophosphate, triphenyl phosphite, polybutenyl succinimide, and succinic acid ester containing 6% by mass of a package additive. And 6% by mass of polymethacrylate viscosity index improver added to base oil (mineral oil base oil, kinematic viscosities 5.95mm ² / s @ 100 ° C and 37.5mm ² / s @ 40 ° C) In addition, 0.1% by mass of a polymethacrylate-based pour point depressant and 10 ppm of a silicone-based antifoaming agent as an antifoaming agent were added.

Formulation of Examples and Reference Examples

Formulation of comparative example

比較例のマイクロクラッチ試験測定結果

For the experimental examples, reference examples, and comparative examples, the friction coefficients of sliding speeds of 3 mm / s and 38 mm / s were measured at oil temperatures of 40 ° C. and 80 ° C. The results are shown in Tables 4 and 5.
Example and reference microclutch test measurement results

Microclutch test measurement results of comparative example

Looking at the test results at 40 ° C., Comparative Example 1 of a commercial tractor oil has a friction coefficient μs (3 mm / s) of 0.108, μd (38 mm / s) of 0.117, and μs / μd. Although the ratio was 0.923, when the mixed diol of C14 and C16 of Reference Example 1 was added, μs became 0.082, μd became 0.113, and the ratio of μs / μd was as low as 0.726, so that the static friction was low. It becomes low and it turns out that the anti-stick slip in a wet clutch is suppressed. Further, C16 1,2-hexadecanediol has a ratio of μs / μd of 0.741, and C12 dodecanediol has a low value of 0.739, both of which give good friction characteristics. One C16 1-hexadecanol has a ratio of μs / μd of 0.862, 1-dodecanol is 0.802, and 1-octanediol is 0.808, which is lower than the commercial tractor oil of Comparative Example 1. Although the ratio was μs / μd, the ratio was higher than that of the reference example.
Similarly, considering the results at 80 ° C., the ratios of μs / μd in Reference Examples 1, 2, and 3 are 0.694, 0.692, and 0.692, respectively, whereas Comparative Examples 1, 2, and The μs / μd ratios of 3, 4, and 5 were 0.731, 0.764, 0.736, 0.716, and 0.704, and the reference example showed better friction characteristics as in the case of 40 ° C. It was.
Further, as in Example 1, when the μs / μd ratio at 80 ° C. was 0.659 and diol and dioleyl hydrogen phosphite were combined, the friction characteristics were further improved as compared with the reference example.

Furthermore, in Reference Examples 4 and 5, the addition amount of 1,2-hexadecanediol was added at 0.1 and 0.3 mass%, and the friction behavior was checked. At the same time, the friction behavior was also checked for Example 2 in which 0.2% by mass of dioleyl hydrogen phosphite was added to Reference Example 5.
As a result, in Example 2, the friction characteristics could be further improved than in Reference Examples 4 and 5.

Claims (3)

Mineral oil and synthetic oil as a base oil, (A) 0.01 to 0.3% by mass of an aliphatic 1,2-diol compound represented by the following general formula (Formula 1) based on the total amount of the composition, and (B) The dialkenyl hydrogen phosphite represented by the general formula (Formula 2) is contained in an amount of 0.05 to 5% by mass based on the total amount of the composition, and the ratio of μ3 / μ38 at 40 ° C. in the microclutch test is 0.8 or less. A wet brake lubricating oil composition.
C _n H _2n + _{2 O} 2 or _C n _H 2n _{O 2} (Formula 1)
(The carbon number n is 12 to 16)
(RO) ₂ PH = O (Formula 2)
(R is an alkenyl group having 14 to 18 carbon atoms)   The lubricating oil composition for wet brake according to claim 1, wherein the dialkenyl hydrogen phosphite is dioleyl hydrogen phosphite.   The wet brake lubricating oil composition according to claim 1, further comprising a metal detergent dispersant, an ashless dispersant, a zinc dialkyldithiophosphate, a hindered phenol antioxidant, an amine antioxidant, and a sarcosine A lubricating oil composition for wet brakes containing at least one rust inhibitor, polymethacrylate viscosity improver and silicone antifoaming agent.